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rpm jump when shifting?

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Old Nov 29, 2006 | 08:24 PM
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rpm jump when shifting?

When I'm accelerating quickly, but not WOT, I'm shifting anywhere between 3500 and 4500 rpms. When I push the clutch in the rpms jump up 500 to 1000 rpms and then drop. I'm not leaving my foot on the gas, so thats not it.

Is this something everyone experiences? I have a MBC, and APS BOV.

How can I tell if I have a boost leak with a boost gauge? Someone told me that the APS bov's are known to leak.
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Old Nov 29, 2006 | 08:43 PM
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You find a boost leak with a boost leak tester - the gauge has nothing to do with it. No, APS BOV's are not "known to leak," so that "someone" should become a "no one."

There's no reason for your RPMs to go up that high, and I frankly don't see how they could even have time to shoot up that much unless you take 5 seconds to shift each time. You should probably check your throttle cable if the RPMs go up when NOT touching the gas and when NOT IN GEAR, because that shouldn't happen. If the RPMs shoot up when accelerating in that area, then it's the clutch, but that isn't how you described the situation.
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Old Nov 29, 2006 | 08:51 PM
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No, I don't take 5 secs. to shift, but I don't quickly throw it gear either. Its only when I shift while accelerating quickly. If I'm in say 2nd gear, I can hold it steady at 4000 for a few secs. and then shift, it won't do it. Only while accelerating.
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Old Nov 29, 2006 | 09:00 PM
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Sounds like momentum of the flywheel from letting your foot off the gas a split second after depressing the clutch.
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Old Nov 29, 2006 | 09:37 PM
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Ok, I just took it out for a few tests. When the rpms jump like that, there is no blow off sound. When it doesn't jump, the blow off is a quick snap or sneeze.

rpm jump = no bov snap or sound is low
no rpm jump = quick bov snap

Out of curiousity, what is this bov flutter.

My friend has a stock 8 dv laying around. I might ask him if I could use it for a few days to see if this jump stops with it in. BTW I bought the car with the APS in it.
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Old Nov 30, 2006 | 05:36 AM
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Originally Posted by Warrtalon
Sounds like momentum of the flywheel from letting your foot off the gas a split second after depressing the clutch.
Listen to this man, he is smart, or your still depressing the gas pedal for a split second after you release the clutch.
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Old Nov 30, 2006 | 07:59 AM
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Originally Posted by Warrtalon
Sounds like momentum of the flywheel from letting your foot off the gas a split second after depressing the clutch.

I think Warr is on to somthing here mine VIII used to keep rpm or slightly raise between shifts onlywhen getting on it hard. It has not done it since I replaced the clutch and flywheel
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Old Nov 30, 2006 | 11:40 AM
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Ok. Thanks guys. Its not a big deal or anything. It's just annoying. I'm not leaving my foot on the gas for a split second. I tested that theory last night.
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Old Nov 30, 2006 | 12:51 PM
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Last edited by dustink; Jan 29, 2007 at 11:29 AM.
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Old Nov 30, 2006 | 01:32 PM
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Originally Posted by dustink
I am dealing with a similar problem. The throttle acts as if it is sticking during high rpm (>4k rpm) stints. For example if I rev out a gear going WOT, say first gear, then put the clutch in and shift into neutral, the revs will drop VERY VERY slowly and it takes a couple pumps of the clutch to get the revs to fall normally. It's a PITA to say the least and makes high-rpm shifting tedious.

Dustin
Clutch pedal sensor disconnected? I know that causes the symptoms you are describing.
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Old Nov 30, 2006 | 07:03 PM
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Originally Posted by PessimiStick
Clutch pedal sensor disconnected? I know that causes the symptoms you are describing.
Would that be located down around the clutch pedal under the dash?
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Old Nov 30, 2006 | 07:20 PM
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My problem is the like the one discussed in this thread: https://www.evolutionm.net/forums/sh...d.php?t=217084
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Old Nov 30, 2006 | 07:30 PM
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I had the same problem and i swore i was not still touching the gas for a split second...but guess what i was my foot did not leave the pedal completely in time. befor i depressed the clutch....It was all about the timeing...you will get it.... it just takes time, you will then become one with the EVO!!!!!
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Old Dec 1, 2006 | 06:51 AM
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Originally Posted by cableguy5752
Would that be located down around the clutch pedal under the dash?
Well I was more asking if you removed it knowingly and didn't know it could cause the issue you're seeing. I doubt it just fell off. =)

I think there's a how-to for disconnecting it, but yes, the plug is under the dash near the pedal.
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Old Dec 1, 2006 | 07:45 AM
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Last edited by dustink; Jan 29, 2007 at 11:28 AM.
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